1. Field of the Invention
The present invention relates to a fuse structure incorporated in an internal wiring of a semiconductor device and cut as required for modifying a circuit pattern of the semiconductor device.
2. Description of the Related Art
A semiconductor device provided with a fuse and a fuse structure therefor are disclosed in Japanese Unexamined Patent Publication (Kokai) No. 57-72368.
The fuse in the semiconductor device is typically formed of a polycrystalline silicon and have a planar configuration as illustrated in FIG. 5, for example. Namely, the fuse has a relatively elongated fuse body 110 and connecting end electrode portions 112 and 114 integrally formed at both ends of the fuse body 110. Respective of the connecting end electrode portions 112 and 114 are connected to internal aluminum wirings of the semiconductor device, for example.
For cutting the fuse, two ways are typically used. One is the method employing a laser beam, in which the laser beam is irradiated at the fuse body 110 of the fuse to be cut to fuse the fuse body 110 by the laser beam. The other method is to charge a high fusing voltage between the connecting end electrode portions 112 and 114 at both ends of the fuse for electrically fusing the fuse body 110 by heating through a resistance heating.
The fuse incorporated in the internal wiring of the semiconductor device is covered with a passivation layer. Either in case of fusing the fuse employing the laser beam or in case of fusing the fuse electrically, an opening 115 is frequently formed in the passivation layer at the portion corresponding to the fuse body 110 for discharging the vaporized silicon.
When the fuse is to be molten electrically by resistance heating, the high fusing voltage is applied to the connecting end electrode portions 112 and 114 at both ends of the fuse to be molten, as set forth above. However, since the fuse is also connected to other circuit portions of the semiconductor device, the voltage to be charged is limited. The limit of the voltage to be charged is normally 10.about.15V. Therefore, in the conventional structure of the fuse, the fuse body 110 is not sufficient and cannot assure fusing thereof.
As a solution to this, it is considered making the fuse body 110 thinner to increase the resistance thereof. However, when the fuse remains conductive without cutting, a current may constantly flow therethrough during normal use of the semiconductor device to cause fusing of the fuse during operation of the semiconductor device if the fuse is excessively thin. Therefore, there is also a limit in thinning the fuse.
Therefore, it is an object of the present invention to provide a fuse structure for a semiconductor device that can be molten electrically by resistance heating.